Distance image capturing device, distance image capturing method, and program

Abstract

A distance image processing unit executes either the normal mode or a power saving mode having lower power consumption than the normal mode, in the power saving mode, accumulates the charge in the charge accumulation unit at a frequency which is the same as that in the normal mode or smaller than that in the normal mode, determines whether or not a moving object is present in the space, and releases the power saving mode as satisfying a return condition in a case where the moving object is present in the space, and determines whether a moving object is present in the space according to the amount of charge accumulated in each of the charge accumulation units in the normal mode, and shifts to the power saving mode in a case where determining that the moving object is not present in the space.

What is claimed is: 
     
         1 . A distance image capturing device comprising:
 a light source unit configured to emit an optical pulse to a space which is a capturing target;   a light receiving unit configured to include a pixel having a photoelectric conversion element which generates a charge according to a light incident from the space and a plurality of charge accumulation units that accumulate the charge, and a pixel driving circuit which performs driving for accumulating the charge in each of the charge accumulation units to accumulate the charge; and   a distance image processing unit configured to control the pixel driving circuit, accumulate the charge in each of the charge accumulation units at an accumulation timing synchronized with an emission timing of emitting the optical pulse in a normal mode, and calculate a distance to a subject present in the space based on an amount of charge accumulated in each of the charge accumulation units, wherein   the distance image processing unit   executes either the normal mode or a power saving mode having lower power consumption than the normal mode,   in the power saving mode, accumulates the charge in the charge accumulation unit at a frequency which is the same as that in the normal mode or smaller than that in the normal mode, determines whether or not a moving object is present in the space according to the amount of charge accumulated in the charge accumulation unit, and releases the power saving mode as satisfying a return condition in a case where the moving object is present in the space, and   determines whether a moving object is present in the space according to the amount of charge accumulated in each of the charge accumulation units in the normal mode, and shifts to the power saving mode in a case where the distance image processing unit is determined that the moving object is not present in the space.   
     
     
         2 . The distance image capturing device according to  claim 1 , wherein
 the distance image processing unit executes the power saving mode when the distance image capturing device is activated.   
     
     
         3 . The distance image capturing device according to  claim 1 , wherein
 in the power saving mode, the distance image processing unit stops emitting the optical pulse, accumulates the charge in each of the charge accumulation units, and determines whether or not a moving object is present in the space according to a change in a pixel value corresponding to an amount of light received by a pixel receiving an external light.   
     
     
         4 . The distance image capturing device according to  claim 1 , wherein
 in the power saving mode, the distance image processing unit sets a frequency of emitting the optical pulse to be smaller than that in the normal mode, accumulates the charge in each of the charge accumulation units at the accumulation timing, and determines whether or not a moving object is present in the space according to a change in a pixel value corresponding to an amount of light received by a pixel receiving a reflected light of the optical pulse.   
     
     
         5 . The distance image capturing device according to  claim 1 , wherein
 in the power saving mode, the distance image processing unit sets a frequency of emitting the optical pulse to be smaller than that in the normal mode, accumulates the charge in each of the charge accumulation units at the accumulation timing, and determines whether or not a moving object is present in the space according to a change in the amount of charge accumulated in the charge accumulation unit.   
     
     
         6 . The distance image capturing device according to  claim 1 , wherein
 in the power saving mode, the distance image processing unit sets a frequency of emitting the optical pulse to be smaller than that in the normal mode, delays an emission timing of emitting the optical pulse compared to the normal mode, accumulates the charge in each of the charge accumulation units at the accumulation timing, and determines whether or not a moving object is present in the space according to a change in the amount of charge accumulated in the charge accumulation unit.   
     
     
         7 . The distance image capturing device according to  claim 1 , wherein
 in the power saving mode, the distance image processing unit performs the driving for a smaller number of pixels than that in the normal mode, and determines whether or not a moving object is present in the space according to a change in the amount of charge accumulated in the charge accumulation unit of the pixel subjected to the driving.   
     
     
         8 . The distance image capturing device according to  claim 7 , wherein
 the distance image processing unit performs the driving on a plurality of pixels, calculates the number of pixels with high pixel values, which is the number of pixels where a pixel value is a first threshold value or greater among the pixels subjected to the driving, and determines that the moving object is present in the space in a case where a difference between the number of pixels with high pixel values in current driving and the number of pixels with high pixel values in previous driving is a second threshold value or greater.   
     
     
         9 . The distance image capturing device according to  claim 7 , wherein
 a plurality of pixels are arranged in a two-dimensional matrix, and   the distance image processing unit performs the driving on the plurality of pixels, calculates an addition value obtained by adding each of pixel values of the pixels arranged along a specific direction among the pixels subjected to the driving, and determines that the moving object is present in the space in a case where the number of specific directions in which a difference between the addition value in the current driving and the addition value in the previous driving is a third threshold value or greater is a fourth threshold value or greater.   
     
     
         10 . The distance image capturing device according to  claim 9 , wherein
 the distance image processing unit determines that the moving object is present in the space using a pixel value of a pixel obtained by regarding the plurality of pixels as one pixel by combining the plurality of pixels subjected to the driving, or a pixel value of a part of pixels among the plurality of pixels subjected to the driving.   
     
     
         11 . The distance image capturing device according to  claim 9 , wherein
 the distance image processing unit performs edge detection on an image including the pixel subjected to the driving, and calculates the addition value using a binarized image according to whether or not the pixel is a pixel in which an edge is detected.   
     
     
         12 . The distance image capturing device according to  claim 8 , wherein
 the distance image processing unit determines that the moving object is present in the space using a pixel value corresponding to an amount of charge accumulated in one specific charge accumulation unit provided in the pixel, or a pixel value corresponding to an amount of light of a reflected light of the optical pulse incident on the pixel.   
     
     
         13 . The distance image capturing device according to  claim 1 , wherein
 a reflecting object is installed in the space, and   in the power saving mode, the distance image processing unit sets a frequency of emitting the optical pulses to be smaller than that in the normal mode, and determines whether or not a moving object is present in the space according to a change in a pixel value corresponding to an amount of light received by a pixel receiving a light arriving from the reflecting object.   
     
     
         14 . The distance image capturing device according to  claim 1 , wherein
 a light-emitting object is installed in the space, and   in the power saving mode, the distance image processing unit stops emitting the optical pulse, and determines whether or not a moving object is present in the space according to a change in a pixel value corresponding to an amount of light received by a pixel receiving a light arriving from the light-emitting object.   
     
     
         15 . The distance image capturing device according to  claim 1 , wherein
 the distance image processing unit performs a pre-operation drive after releasing the power saving mode, in the pre-operation drive, causes each of the charge accumulation units to accumulate the charge at the accumulation timing, determines whether or not a moving object is present in the space according to the amount of charge accumulated in each of the charge accumulation units, shifts to the normal mode in a case where the moving object is detected within a predetermined time in the pre-operation drive, and shifts to the power saving mode in a case where the moving object is not detected within a predetermined time in the pre-operation drive.   
     
     
         16 . The distance image capturing device according to  claim 1 , wherein
 the distance image processing unit performs a high-speed drive after releasing the power saving mode, in the high-speed drive, increases a frequency of emitting the optical pulse compared to the normal mode, causes each of the charge accumulation units to accumulate the charge at the accumulation timing, calculates the distance to the subject present in the space based on the amount of charge accumulated in each of the charge accumulation units, and shifts to the normal mode after performing the high-speed drive for a predetermined time.   
     
     
         17 . The distance image capturing device according to  claim 1 , wherein
 in the power saving mode, the distance image processing unit releases the power saving mode in a case where a control signal for releasing the power saving mode is acquired from an external device.   
     
     
         18 . A distance image capturing method performed by a distance image capturing device including a light source unit configured to emit an optical pulse to a space which is a capturing target, a light receiving unit configured to include a pixel having a photoelectric conversion element which generates a charge according to a light incident from the space and a plurality of charge accumulation units that accumulate the charge, and a pixel driving circuit which performs driving for accumulating the charge in each of the charge accumulation units, and a distance image processing unit configured to control the pixel driving circuit, accumulates the charge in each of the charge accumulation units at an accumulation timing synchronized with an emission timing of emitting the optical pulse in a normal mode, and calculates a distance to a subject present in the space based on an amount of charge accumulated in each of the charge accumulation units, the method comprising:
 via the distance image processing unit,   executing either the normal mode or a power saving mode having lower power consumption than the normal mode,   in the power saving mode, accumulating the charge in the charge accumulation unit at a frequency which is the same as that in the normal mode or smaller than that in the normal mode, determining whether or not a moving object is present in the space according to the amount of charge accumulated in the charge accumulation unit, and releasing the power saving mode as satisfying a return condition in a case where the moving object is present in the space, and   determining whether a moving object is present in the space according to the amount of charge accumulated in each of the charge accumulation units in the normal mode, and shifting to the power saving mode in a case where the distance image processing unit is determined that the moving object is not present in the space.   
     
     
         19 . A non-transitory computer-readable storage medium storing a program for causing a computer of a distance image capturing device including a light source unit configured to emit an optical pulse to a space which is a capturing target, a light receiving unit configured to include a pixel having a photoelectric conversion element which generates a charge according to a light incident from the space and a plurality of charge accumulation units that accumulate the charge, and a pixel driving circuit which performs driving for accumulating the charge in each of the charge accumulation units, and a distance image processing unit configured to control the pixel driving circuit, accumulates the charge in each of the charge accumulation units at an accumulation timing synchronized with an emission timing of emitting the optical pulse in a normal mode, and calculates a distance to a subject present in the space based on an amount of charge accumulated in each of the charge accumulation units, to execute a process comprising:
 executing either the normal mode or a power saving mode having lower power consumption than the normal mode,   in the power saving mode, accumulating the charge in the charge accumulation unit at a frequency which is the same as that in the normal mode or smaller than that in the normal mode, determining whether or not a moving object is present in the space according to the amount of charge accumulated in the charge accumulation unit, and releasing the power saving mode as satisfying a return condition in a case where the moving object is present in the space, and   determining whether a moving object is present in the space according to the amount of charge accumulated in each of the charge accumulation units in the normal mode, and shifting to the power saving mode in a case where the distance image processing unit is determined that the moving object is not present in the space.   
     
     
         20 . The distance image capturing device according to  claim 9 , wherein
 the distance image processing unit determines that the moving object is present in the space using a pixel value corresponding to an amount of charge accumulated in one specific charge accumulation unit provided in the pixel, or a pixel value corresponding to an amount of light of a reflected light of the optical pulse incident on the pixel.